Yeah the reverse lock-out collar won't let me go any further than that. Without cutting it, I really can't see a way around it.
Edit: So I emailed them, and this is the response.
"Hello!
that is normal. Since the boot you have ordered is tight on top, the sewing machine won't go all the way in - it's header has a certain size and it just won't get anywhere.
This is NORMAL with the kind of boot that you have.
Please just try to install it so that the shorter stitched edge faces the FRONT of the car. This way you will not be able to see it while you're in the driver's or passengers seat and it'll look perfect."
The shift boot doesn't quite go around that way...well this was my feeler for the rest of their products, not looking very good so far.